Such an exhaust manifold, which in principle can also be designated as an exhaust plenum chamber, is known, for example, from DE 10 2005 025 735 B3 and comprises a housing from which a plurality of inlet pipes emanate, which, in the built-in state, lead to cylinders of the internal combustion engine and a flange, which is welded to the inlet pipes and which, in the built-in state, is screwed to the cylinder head of the internal combustion engine by means of screws. The known exhaust manifold is further configured as an air-gap-isolated exhaust manifold, whose housing together with the inlet pipes is formed by an inner shell and an outer shell, which are both welded to the flange and between which an isolating air gap is formed.
During operation of an internal combustion engine, the exhaust manifold frequently reaches significantly higher temperatures than the cylinder head. This leads to different thermal expansions, which is clearly noticeable particularly in a longitudinal direction of the exhaust manifold, especially in in-line engines having four or more cylinders.
In principle, it is possible to design the screw connection of the flange to the cylinder head in such a manner that a thermally induced relative movement between flange and cylinder head is minimized. In this case, however, extreme stresses are formed in the housing, which can comparatively rapidly lead to fatigue or even to rupture of the material. Likewise, it is fundamentally possible to configure the screw connection in such a manner that the flange can move in a thermally induced manner comparatively freely relative to the cylinder head, i.e., it can slide in a contact plane between flange and cylinder head. As a result, a relative change in position between the inlet pipes and the cylinders comes about, which is disadvantageous for the sealing and unfavorable for the flow conditions.